/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch licenses this file to you under
 * the Apache License, Version 2.0 (the "License"); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.elasticsearch.spark.sql.streaming

import org.apache.spark.sql.execution.streaming.MetadataLog

/**
 * A null object style metadata log that discards incoming data, and otherwise
 * acts like an empty log.
 */
class NullMetadataLog[T] extends MetadataLog[T] with Serializable {

  // Always return successful storage
  override def add(batchId: Long, metadata: T): Boolean = true

  override def get(batchId: Long): Option[T] = None

  override def get(startId: Option[Long], endId: Option[Long]): Array[(Long, T)] = Array()

  override def getLatest(): Option[(Long, T)] = None

  override def purge(thresholdBatchId: Long): Unit = ()

}
